Effect of Different Types of Overvoltage Protective Devices Against Vacuum Circuit-Breaker-Induced Transients in Cable Systems

Transient overvoltages due to circuit-breaker switching may occur if certain conditions regarding system layout and type of switching operations are fulfilled. In such applications, overvoltage protection should be used. Different types of protective devices exist, such as surge arresters and RC snubbers, and they can be installed in different configurations. The purpose of the presently published results is to show the effect of the different protective devices. Laboratory testing has been performed, focusing on the disconnection of an inductively loaded transformer at a phase angle causing multiple reignitions. It was found that surge arresters limit the voltages to well-defined amplitudes, but a number of reignitions occur up to this level. RC snubbers, on the other hand, reduce the risk of having reignitions and the number of reignitions in case they do occur, but the voltages are not limited at well-defined amplitudes. All of the tested configurations of protective devices limited the voltages below the basic insulation level of the transformer.